The program deals with chemical, physical and biological factors in the causation of cancer as well as their interaction. The approaches described cover a wide range and include biochemical studies of intracellular mechanisms including cell kinetics, the development of laboratory models for cancer in various organ systems, the development of mathematical models for cancer induction, and epidemiological studies on human populations aimed at the identification of causal factors. The present program involves three elements: 1) expansion of ongoing research, 2) the development of new lines of study within existing laboratories of the Institute and 3) development of two new divisions within the Institute, a Laboratory of Experimental Pathology and Laboratory of Immunology. Clearly, cancer prevention is a most desirable means for the control of cancer. It is believed that there are solid leads which promise practical results in the attainment of means for the prevention or reduction of some forms cancer. The Center Grant would be used primarily for the core support (senior staff, seed money for exploratory projects, key equipment and central services). The major supporting funds would be sought through the usual grant and contract sources. This application proposes the re- establishment of the joint participation in the Center Grant of the National Cancer Institute with the National Institute of Environmental Health Sciences.